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copied!<p>I need to find whether a class have implemented a specific interface(suppose java.io.Serializable)</p> <p>following is my code</p> <pre><code>class Employee{},class Test implements java.io.Serializable{},class Point{}, class Main{}, class MyApp{},class TestApp implements java.io.Serializable{}; class MyMain { public static void main(String[] args) { String[] classes={"Employee","Test","Point","Main","MyApp"}; // array of class names in default package Class interFace = Class.forName("java.io.Serializable"); for(int i=0 ;i < classes.length;i++) { Class clas = Class.forName(classes[i]); boolean match = !clas.isInterface() && !clas.isEnum() && interFace.isAssignableFrom(clas) ; if(match ) { System.out.println(classes[i]+ "implements java.io.Serializable"); }}}} </code></pre> <p><strong>Output</strong></p> <p>Employee implements java.io.Serializable /// wrong</p> <p>Test implements java.io.Serializable /// correct</p> <p>Main implements java.io.Serializable /// wrong</p> <p>TestApp implements java.io.Serializable /// correct</p> <p><strong>Problem</strong></p> <p>Problem is only with Employee and Main class when they are in default package.</p> <h2>I donot understand why this happen?</h2> <pre><code>public class JarFileLoader extends URLClassLoader { public JarFileLoader (URL[] urls) { super (urls); } public void addFile (String path) throws MalformedURLException { String urlPath = "jar:file:/" + path + "!/"; addURL (new URL (urlPath)); } } </code></pre> <hr> <pre><code>class JarUtils { public static List getClasseNamesInJAR(String jarName) throws Exception { ArrayList classes = new ArrayList(); try { JarInputStream jarFile = new JarInputStream(new FileInputStream(jarName)); JarEntry jarEntry; while (true) { jarEntry = jarFile.getNextJarEntry(); if (jarEntry == null) break; if (jarEntry.isDirectory()) continue; if ((jarEntry.getName().endsWith(".class"))) { classes.add(jarEntry.getName().replaceAll("/", "\\.")); } } return classes; } catch (Exception e) { throw e; } } } </code></pre> <hr> <pre><code>public class ClassImplementer { private List getClasses(String path, String interfaceName) throws Exception { List list = new ArrayList(); if (path.endsWith(".jar")) { List l = JarUtils.getClasseNamesInJAR(path); if(l!=null && l.size()<=0) return null; try { URL urls[] = {}; JarFileLoader cl = new JarFileLoader(urls); cl.addFile(path); Class interFace = Class.forName(interfaceName); for (int i = 0; i < l.size(); i++) { String[] tempClass = l.get(i).toString().split(".class"); Class clas = cl.loadClass(tempClass[0]); boolean match = !clas.isInterface() && !clas.isEnum() && interFace.isAssignableFrom(clas) ; if(match ) { list.add(tempClass[0]); } } return list; } catch (Exception ex) { throw ex; } return list; } } public class Test{ public static void main(String[] args) ClassImplementer imp=new ClassImplementer(); try{ List l=imp.getClasses("c:/abc.jar","java.io.Serializable"); for(int i=0;i<l.size();i++)System.out.println(l.get(i)+" implements java.io.Serializable"); }catch(Exception ex){} } </code></pre>

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